In a conventional four-wheeled vehicle which is steerable only by the front wheels, a disagreement in the trajectories 4 and 5 of, for instance, the inner front wheel 2 and the inner rear wheel 3, or a socalled inner radius difference, arises when the vehicle makes a turn about a point 0 as shown in FIG. 1 (the arrow F indicates the direction of the movement of the vehicle). The outer wheels also have a similar difference in trajectory as the vehicle makes a turn although the difference is slightly smaller than the inner radius difference because of the difference in the effective wheel bases of the inner and outer wheel pairs. Therefore, even when the front part of the vehicle has managed to go through a narrow point of the road, the rear part of the vehicle may not be able to do so without deviating from the prescribed course of the road or hitting a wall if the road is surrounded by such a wall on either side. It is thus known that there is a problem in the handling of conventional vehicles when they move through a narrow and tortuous part of a road.
Based upon this recognition, there has been proposed the front and rear wheel steering vehicle which steers the front and rear wheels 2 and 3 by the same angle and in the opposite phase relationship as shown in FIG. 2. According to this vehicle, since the trajectories 4 and 5 of the front and rear wheels agree during a steady turning maneuver, the handling of the vehicle is substantially improved over the conventional vehicles which are steerable only by the front wheels.
However, even in this front and rear wheel steering vehicle, the inner radius difference becomes zero only when the vehicle makes a steady turn; as shown in FIG. 3, when the vehicle makes a right steady turn about a point O.sub.1, with the vehicle body 1 changing its position from the position I to the position II, followed by a steady left turn about a point O.sub.2 towards the position III, the trajectories 4 and 5 of the front and rear wheels 2 and 3 disagree from each other and the effect of improving the handling of the vehicle becomes insufficient whenever the direction of the turning motion is changed. In reality, since the steer angle is changed continually, the rear wheels move along trajectories which deviate from those of the front wheels in a highly complicated manner.